Method And Apparatus For Single Network Slice Selection Assistance Information Based Congestion Control In Mobile Communications

ABSTRACT

Various solutions for single network slice selection assistance information (S-NSSAI) based congestion control with respect to user equipment and network apparatus in mobile communications are described. An apparatus may receive a message with a back-off timer from the network node. The apparatus may determine whether an S-NSSAI of a protocol data unit (PDU) session is provided by the network node. The apparatus may start the back-off timer and associate the back-off timer with the S-NSSAI of the PDU session in an event that the S-NSSAI is provided by the network node.

CROSS REFERENCE TO RELATED PATENT APPLICATION(S)

The present disclosure claims the priority benefit of U.S. ProvisionalPatent Application No. 62/888,145, filed on 16 Aug. 2019, and U.S.Provisional Patent Application No. 62/907,918, filed 30 Sep. 2019. Thecontents of aforementioned applications are herein incorporated byreference in their entirety.

TECHNICAL FIELD

The present disclosure is generally related to mobile communicationsand, more particularly, to single network slice selection assistanceinformation (S-NSSAI) based congestion control enhancement with respectto user equipment and network apparatus in mobile communications.

BACKGROUND

Unless otherwise indicated herein, approaches described in this sectionare not prior art to the claims listed below and are not admitted asprior art by inclusion in this section.

5^(th) generation system (5GS) networks are packet-switched (PS)Internet Protocol (IP) networks. This means that the networks deliverall data traffic in IP packets, and provide users with always-on IPconnectivity. When the UE joins a 5GS network, a packet data network(PDN) address (i.e., the one that can be used on the PDN) is assigned tothe UE for its connection to the PDN. In 4G, EPS has defined a defaultEPS bearer to provide the IP connectivity that is always-on. In 5G, aprotocol data unit (PDU) session establishment procedure is a parallelprocedure of a PDN connection procedure in 4G. A PDU session defines theassociation between the UE and the data network that provides a PDUconnectivity service. Each PDU session is identified by a PDU sessionID, and may include multiple quality of service (QoS) flows and QoSrules.

The 5GS supports network slicing as described in 3^(rd) GenerationPartnership Project (3GPP) Technical Specification (TS) 23.501. Anetwork slice may be viewed as a logical end-to-end network that can bedynamically created and can provide specific network capabilities andnetwork characteristics. A given UE may access to multiple slices overthe same Access Network (e.g. over the same radio interface). Each slicemay serve a particular service type. A network slice is defined within apublic land mobile network (PLMN) and includes the core network controlplane and user plane network functions as well as the 5G access network(AN). Within a PLMN or stand-alone non-public networks (SNPN), a networkslice is identified by an S-NSSAI, which is comprised of a slice/servicetype (SST) and a slice differentiator (SD). Inclusion of an SD in anS-NSSAI may be optional. A set of one or more S-NSSAIs is called theNSSAI. The S-NSSAI may be signaled by the UE to the network to assistthe network in selecting a particular network slice instance.

It was agreed that the S-NSSAI value of a PDU session can be updated,(e.g., when the UE moves to a different PLMN), thus the S-NSSAI of aserving PLMN associated with a PDU session may be changed during the PDUsession lifetime (e.g., after inter-PLMN change). Therefore, regardingS-NSSAI based congestion control, it seems to be not appropriate toalways associate the S-NSSAI based back-off timer with the S-NSSAIprovided by the UE during the PDU session establishment. If the S-NSSAIbased back-off timer does not be associated to an appropriate S-NSSAIvalue when inter-PLMN change occurs, the congestion control mechanismcould be executed incorrectly. Therefore, the S-NSSAI-based congestioncontrol mechanism may need update accordingly.

Accordingly, how to design and enhance the S-NSSAI-based congestioncontrol mechanism becomes an important issue in the newly developedwireless communication network. Therefore, there is a need to provideproper schemes to associate the S-NSSAI based back-off timer with anappropriate S-NSSAI.

SUMMARY

The following summary is illustrative only and is not intended to belimiting in any way. That is, the following summary is provided tointroduce concepts, highlights, benefits and advantages of the novel andnon-obvious techniques described herein. Select implementations arefurther described below in the detailed description. Thus, the followingsummary is not intended to identify essential features of the claimedsubject matter, nor is it intended for use in determining the scope ofthe claimed subject matter.

An objective of the present disclosure is to propose solutions orschemes that address the aforementioned issues pertaining to S-NSSAIbased congestion control enhancement with respect to user equipment andnetwork apparatus in mobile communications.

In one aspect, a method may involve an apparatus receiving a messagewith a back-off timer from a network node. The method may also involvethe apparatus determining whether an S-NSSAI of a PDU session isprovided by the network node. Then, the method may involve the apparatusstarting the back-off timer and associating the back-off timer with theS-NSSAI of the PDU session in an event that the S-NSSAI is provided bythe network node.

In one aspect, a method may involve an apparatus receiving a messagewith a back-off timer from a network node. The method may also involvethe apparatus starting the back-off timer associated with an S-NSSAI ofa PDU session. The method may further determining whether an S-NSSAI ofa request message is the S-NSSAI associated with the back-off timerinvolve the apparatus. Then, the method may involve the apparatusforbidding a transmission of the request message in an event that theS-NSSAI of the request message is the S-NSSAI associated with theback-off timer.

In one aspect, an apparatus may comprise a transceiver which, duringoperation, wirelessly communicates with a network node of a wirelessnetwork. The apparatus may also comprise a processor communicativelycoupled to the transceiver. The processor, during operation, may performoperations comprising receiving, via the transceiver, a message with aback-off timer from a network node. The processor may also performoperations comprising determining whether an S-NSSAI of a PDU session isprovided by the network node. The processor may further performoperations comprising starting the back-off timer and associating theback-off timer with the S-NSSAI of the PDU session in an event that theS-NSSAI is provided by the network node.

In one aspect, an apparatus may comprise a transceiver which, duringoperation, wirelessly communicates with a network node of a wirelessnetwork. The apparatus may also comprise a processor communicativelycoupled to the transceiver. The processor, during operation, may performoperations comprising receiving, via the transceiver, a message with aback-off timer from a network node. The processor may also performoperations comprising starting the back-off timer associated with anS-NSSAI of a PDU session. The processor may further perform operationscomprising determining whether an S-NSSAI of a request message is theS-NSSAI associated with the back-off timer involve the apparatus. Theprocessor may further perform operations comprising forbidding atransmission of the request message in an event that the S-NSSAI of therequest message is the S-NSSAI associated with the back-off timer.

It is noteworthy that, although description provided herein may be inthe context of certain radio access technologies, networks and networktopologies such as Long-Term Evolution (LTE), LTE-Advanced, LTE-AdvancedPro, 5th Generation (5G), New Radio (NR), Internet-of-Things (IoT),Narrow Band Internet of Things (NB-IoT) and Industrial Internet ofThings (IIoT), the proposed concepts, schemes and anyvariation(s)/derivative(s) thereof may be implemented in, for and byother types of radio access technologies, networks and networktopologies. Thus, the scope of the present disclosure is not limited tothe examples described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of the present disclosure. The drawings illustrate implementationsof the disclosure and, together with the description, serve to explainthe principles of the disclosure. It is appreciable that the drawingsare not necessarily in scale as some components may be shown to be outof proportion than the size in actual implementation in order to clearlyillustrate the concept of the present disclosure.

FIG. 1 is a diagram depicting an exemplary 5G network in accordance withimplementations of the present disclosure.

FIG. 2 is tables illustrating the content of S-NSSAI information elementand SST values as defined in 3GPP specification.

FIG. 3 is a diagram depicting an example scenario under schemes inaccordance with implementations of the present disclosure.

FIG. 4 is a diagram depicting an example scenario under schemes inaccordance with implementations of the present disclosure.

FIG. 5 is a diagram depicting an example scenario under schemes inaccordance with implementations of the present disclosure.

FIG. 6 is a diagram depicting an example scenario under schemes inaccordance with implementations of the present disclosure.

FIGS. 7A-7B are diagrams depicting an example scenario under schemes inaccordance with implementations of the present disclosure.

FIGS. 8A-8B are diagrams depicting an example scenario under schemes inaccordance with implementations of the present disclosure.

FIG. 9 is a diagram depicting an example scenario under schemes inaccordance with implementations of the present disclosure.

FIG. 10 is a block diagram of an example communication apparatus and anexample network apparatus in accordance with an implementation of thepresent disclosure.

FIG. 11 is a flowchart of an example process in accordance with animplementation of the present disclosure.

FIG. 12 is a flowchart of an example process in accordance with animplementation of the present disclosure.

FIG. 13 is a flowchart of an example process in accordance with animplementation of the present disclosure.

FIG. 14 is a flowchart of an example process in accordance with animplementation of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED IMPLEMENTATIONS

Detailed embodiments and implementations of the claimed subject mattersare disclosed herein. However, it shall be understood that the disclosedembodiments and implementations are merely illustrative of the claimedsubject matters which may be embodied in various forms. The presentdisclosure may, however, be embodied in many different forms and shouldnot be construed as limited to the exemplary embodiments andimplementations set forth herein. Rather, these exemplary embodimentsand implementations are provided so that description of the presentdisclosure is thorough and complete and will fully convey the scope ofthe present disclosure to those skilled in the art. In the descriptionbelow, details of well-known features and techniques may be omitted toavoid unnecessarily obscuring the presented embodiments andimplementations.

Overview

Implementations in accordance with the present disclosure relate tovarious techniques, methods, schemes and/or solutions pertaining toS-NSSAI based congestion control with respect to user equipment andnetwork apparatus in mobile communications. According to the presentdisclosure, a number of possible solutions may be implemented separatelyor jointly. That is, although these possible solutions may be describedbelow separately, two or more of these possible solutions may beimplemented in one combination or another.

FIG. 1 illustrates an exemplary 5G network 100 in accordance withimplementations of the present disclosure. 5G NR network 100 maycomprise a UE 101, a base station gNB 102, an access and mobilitymanagement function (AMF) 103, a session management function (SMF) 104,a policy control function (PCF) 105, and a unified data management (UDM)106. In the example of FIG. 1, UE 101 and its serving base station gNB102 belong to part of a radio access network (RAN) 120. In the accessstratum (AS) layer, RAN 120 may provide radio access for UE 101 via aradio access technology (RAT). In non-access stratum (NAS) layer, AMF103 may communicate with gNB 102, SMF 104, PCF 105 and UDM 106 foraccess and mobility management of wireless access devices in 5G network100. UE 101 may be equipped with a radio frequency (RF) transceiver ormultiple RF transceivers for different application services viadifferent RATs/core networks (CNs). UE 101 may be implemented as a smartphone, a wearable device, an Internet of Things (IoT) device, a tablet,a vehicle, etc.

The 5GS supports network slicing as described in 3GPP TS 23.501. Anetwork slice may be viewed as a logical end-to-end network that can bedynamically created and can provide specific network capabilities andnetwork characteristics. A given UE may access to multiple slices overthe same Access Network (e.g. over the same radio interface). Each slicemay serve a particular service type. A network slice is defined within aPLMN and includes the core network control plane and user plane networkfunctions as well as the 5G AN. Within a PLMN or SNPN, a network sliceis identified by an S-NSSAI, which is comprised of an SST and an SD.Inclusion of an SD in an S-NSSAI may be optional. A set of one or moreS-NSSAIs is called the NSSAI. The S-NSSAI may be signaled by the UE tothe network to assist the network in selecting a particular networkslice instance.

The purpose of the S-NSSAI information element is to identify a networkslice. FIG. 2 illustrates the content of S-NSSAI information element andSST values as defined in 3GPP specification. The S-NSSAI informationelement may comprise the SST and the SD. The SST may refer to theexpected network slice behavior in terms of features and services. TheSD may be an optional information that complements the slice/servicetype(s) to differentiate amongst multiple network slices of the sameslice/service type. The SST may define a plurality of different servicetypes. As shown in FIG. 2, SST value “1” may correspond to a slicesuitable for the handling of 5G enhanced mobile broadband (eMBB). SSTvalue “2” may correspond to a slice suitable for the handling ofultra-reliable low latency communications (URLLC). SST value “3” maycorrespond to a slice suitable for the handling of massive IoT (MIoT).SST value “4” may correspond to a slice suitable for the handling ofvehicle to everything (V2X) services.

It was agreed that the S-NSSAI value of a PDU session can be updated,(e.g., when the UE moves to a different PLMN), thus the S-NSSAI of aserving PLMN associated with a PDU session may be changed during the PDUsession lifetime (e.g., after inter-PLMN change). Therefore, regardingS-NSSAI based congestion control, it seems to be not appropriate toalways associate the S-NSSAI based back-off timer with the S-NSSAIprovided by the UE during the PDU session establishment. If the S-NSSAIbased back-off timer does not be associated to an appropriate S-NSSAIvalue when inter-PLMN change occurs, the congestion control mechanismcould be executed incorrectly. For example, the UE may not be able toforbid 5GSM procedure to the congested network slices. The UE mayincorrectly forbid the 5GSM procedure targeting to a not congestednetwork slice. Therefore, the S-NSSAI-based congestion control mechanismmay need update accordingly, i.e., to associate the back-off timer withthe updated S-NSSAI value instead of always with the S-NSSAI valueprovided by the UE when establishing the PDU session.

In view of the above, the present disclosure proposes a number ofschemes pertaining to S-NSSAI based congestion control enhancement withrespect to the UE and the network apparatus. According to the schemes ofthe present disclosure, after establishing a PDU session, the UE mayproperly update the S-NSSAI when the UE moves to a different PLMN (e.g.,inter-PLMN change). The UE may be able to apply the updated/latestS-NSSAI of the PDU session to the back-off timer for the S-NSSAI basedcongestion control. On the other hand, it is also not clear what is theS-NSSAI value associated with the back-off timer in an event that theback-off timer is applied in all PLMNs. The present disclosure alsodefines the UE handling in roaming and non-roaming scenarios when theback-off timer is applied in all PLMNs. Accordingly, the UE may be ableto apply the back-off timer for the S-NSSAI based congestion controlcorrectly and appropriately.

Specifically, to establish a PDU session in a PLMN, the UE may beconfigured to transmit a PDU session establishment request message tothe network node. The UE may provide a valid S-NSSAI value in the PDUsession establishment request procedure. Then, the UE may receive a PDUsession establishment accept message from the network node. The networknode may provide an S-NSSAI value requested by the UE in the PDU sessionestablishment accept message. The PDU session may be successfullyestablished with the S-NSSAI value requested by the UE. After the PDUsession is established, the UE may move to a different PLMN (e.g.,inter-PLMN change). For example, the UE may transfer from a first PLMNto a second PLMN. At this time, the S-NSSAI of the PDU session may alsobe changed from a first S-NSSAI to a second S-NSSAI. The PDU session nowmay be associated to the second S-NSSAI. The UE may receive the secondS-NSSAI associated with the second PLMN from the network node.

Alternatively, in the PDU session establishment request procedure, theUE may transmit a PDU session establishment request message with noS-NSSAI to the network node. Then, the UE may receive a PDU sessionestablishment accept message from the network node. The network node mayselect and provide an S-NSSAI value to the UE in the PDU sessionestablishment accept message. The PDU session may be successfullyestablished with the S-NSSAI value provided by the network node.Similarly, after the PDU session is established, the UE may move to adifferent PLMN (e.g., inter-PLMN change). For example, the UE maytransfer from a first PLMN to a second PLMN. At this time, the S-NSSAIof the PDU session may also be changed from a first S-NSSAI to a secondS-NSSAI. The PDU session now may be associated to the second S-NSSAI.The UE may receive the second S-NSSAI associated with the second PLMNfrom the network node.

The UE may be configured to transmit a request message to the networknode. The request message may comprise at least one of a PDU sessionestablishment request, a PDU session modification request, and a PDUsession release request. In an event that the network node is in thecongestion status, the UE may receive a message with a congestion causeand a back-off timer for congestion control from the network node. Themessage may comprise at least one of a PDU session establishment reject,a PDU session modification reject, and a PDU session release command.After receiving the message, the UE may be configured to start theback-off timer. The UE may associate the back-off timer with the S-NSSAIin an event that the S-NSSAI is provided by the network node. TheS-NSSAI is the updated/latest S-NSSAI of the current PDU sessionprovided by the network node.

In some implementation, in the PDU session establishment procedure,after transmitting the PDU session establishment request message, the UEmay receive a message with a congestion cause and a back-off timer fromthe network node in an event that the network node is in the congestionstatus. Since the UE only has the S-NSSAI requested by the UE, the UEmay be configured to associate the back-off timer with the S-NSSAIrequested by the UE (e.g., a requested S-NSSAI or no S-NSSAI) in anevent that no S-NSSAI is provided by the network node. The back-offtimer may comprise at least one of a congestion back-off timer T3584 anda congestion back-off timer T3585.

FIG. 3 illustrates an example scenario 300 under schemes in accordancewith implementations of the present disclosure. Scenario 300 involves aUE and a plurality network nodes, which may be a part of a wirelesscommunication network (e.g., an LTE network, an LTE-Advanced network, a5G/NR network, an IoT network, or a V2X network). Scenario 300illustrates which S-NSSAI value the UE should associate with theback-off timer in an event that the UE provides a valid S-NSSAI whenestablishing the PDU session. At first, the UE may register in a firstPLMN (e.g., visited PLMN (VPLMN) 1). The UE may be configured totransmit a PDU session establishment request message to VPLMN 1. The UEmay provide a valid S-NSSAI value (e.g., S-NSSAI_1) to VPLMN 1. Then,VPLMN 1 may transmit a PDU session establishment accept message to theUE. VPLMN 1 may provide the requested S-NSSAI value (e.g., S-NSSAI_1) tothe UE. Thus, the PDU session may be established between the UE andVPLMN 1 with S-NSSAI_1.

The UE may transfer from the first PLMN to a second PLMN (e.g.,inter-PLMN change from VPLMN 1 to VPLMN 2). The S-NSSAI of the PDUsession may be changed from S-NSSAI_1 to S-NSSAI_2. At this moment, thePDU session may be maintained between the UE and VPLMN 2 with S-NSSAI_2.When in the VPLMN 2, the UE may be configured to perform a PDU sessionmodification/release procedure with VPLMN 2. For example, as shown incase 1, the UE may transmit a PDU session modification request messageto VPLM 2. In an event that the network node (e.g., SMF) in VPLMN 2 isin the congestion status, VPLMN 2 may transmit a PDU sessionmodification reject message with a congestion cause. The congestioncause may comprise, for example and without limitation, 5GSM cause value#67 “insufficient resources for specific slice and DNN” or 5GSM causevalue #69 “insufficient resources for specific slice”. After receivingthe congestion cause, the UE may be configured to start a back-offtimer. The back-off timer may comprise the congestion back-off timerT3584 or the congestion back-off timer T3585. The UE may associate theback-off timer with the updated/latest S-NSSAI (e.g., S-NSSAI_2).

In another example, as shown in case 2, the UE may optionally transmit aPDU session release request message to VPLM 2. In an event that thenetwork node (e.g., SMF) in VPLMN 2 is in the congestion status, VPLMN 2may transmit a PDU session release command message with a congestioncause to the UE. Alternatively, the VPLMN may directly transmit the PDUsession release command message to the UE without receiving the PDUsession release request from the UE. Then, the UE may transmit a PDUsession release complete message to VPLMN 2. Similarly, after receivingthe congestion cause, the UE may be configured to start a back-offtimer. The back-off timer may comprise the congestion back-off timerT3584 or the congestion back-off timer T3585. The UE may associate theback-off timer with the updated/latest S-NSSAI (e.g., S-NSSAI_2).

FIG. 4 illustrates an example scenario 400 under schemes in accordancewith implementations of the present disclosure. Scenario 400 involves aUE and a plurality network nodes, which may be a part of a wirelesscommunication network (e.g., an LTE network, an LTE-Advanced network, a5G/NR network, an IoT network, or a V2X network). Scenario 400illustrates which S-NSSAI value the UE should associate with theback-off timer in an event that the UE provides no S-NSSAI whenestablishing the PDU session. At first, the UE may register in a firstPLMN (e.g., VPLMN 1). The UE may be configured to transmit a PDU sessionestablishment request message to VPLMN 1. The UE may provide no S-NSSAIto VPLMN 1 (e.g., the UE does not provide any S-NSSAI value). Then,VPLMN 1 may transmit a PDU session establishment accept message to theUE. VPLMN 1 may select and provide an S-NSSAI value (e.g., S-NSSAI_1) tothe UE. Thus, the PDU session may be established between the UE andVPLMN 1 with S-NSSAI_1.

The UE may transfer from the first PLMN to a second PLMN (e.g.,inter-PLMN change from VPLMN 1 to VPLMN 2). The S-NSSAI of the PDUsession may be changed from S-NSSAI_1 to S-NSSAI_2. At this moment, thePDU session may be maintained between the UE and VPLMN 2 with S-NSSAI_2.When in the VPLMN 2, the UE may be configured to perform a PDU sessionmodification/release procedure with VPLMN 2. For example, as shown incase 1, the UE may transmit a PDU session modification request messageto VPLM 2. In an event that the network node (e.g., SMF) in VPLMN 2 isin the congestion status, VPLMN 2 may transmit a PDU sessionmodification reject message with a congestion cause. The congestioncause may comprise, for example and without limitation, 5GSM cause value#67 “insufficient resources for specific slice and DNN” or 5GSM causevalue #69 “insufficient resources for specific slice”. After receivingthe congestion cause, the UE may be configured to start a back-offtimer. The back-off timer may comprise the congestion back-off timerT3584 or the congestion back-off timer T3585. The UE may associate theback-off timer with the updated/latest S-NSSAI (e.g., S-NSSAI_2).

In another example, as shown in case 2, the UE may optionally transmit aPDU session release request message to VPLM 2. In an event that thenetwork node (e.g., SMF) in VPLMN 2 is in the congestion status, VPLMN 2may transmit a PDU session release command message with a congestioncause to the UE. Alternatively, the VPLMN may directly transmit the PDUsession release command message to the UE without receiving the PDUsession release request from the UE. Then, the UE may transmit a PDUsession release complete message to VPLM 2. Similarly, after receivingthe congestion cause, the UE may be configured to start a back-offtimer. The back-off timer may comprise the congestion back-off timerT3584 or the congestion back-off timer T3585. The UE may associate theback-off timer with the updated/latest S-NSSAI (e.g., S-NSSAI_2). Itshould be noted that, without the enhancement in accordance withimplementations of the present disclosure, the UE will start theback-off timer associated with no S-NSSAI since no S-NSSAI is providedby the UE during the PDU session establishment procedure. Such legacyhandling could cause incorrect congestion control mechanism since theback-off timer is not associated with a proper S-NSSAI.

FIG. 5 illustrates an example scenario 500 under schemes in accordancewith implementations of the present disclosure. Scenario 500 involves aUE and a plurality network nodes, which may be a part of a wirelesscommunication network (e.g., an LTE network, an LTE-Advanced network, a5G/NR network, an IoT network, or a V2X network). Scenario 500illustrates which S-NSSAI value the UE should associate with theback-off timer in an event that the back-off timer is applied in allPLMNs. As mentioned above, an S-NSSAI may comprise the SST and the SD.In the S-NSSAI information element, as shown in FIG. 2, the first SST/SDset is called “serving PLMN S-NSSAI” and the second SST/SD set is called“mapped home PLMN (HPLMN) S-NSSAI”. When the UE is in non-roamingcondition (i.e., attached in HPLMN), the network (i.e., HPLMN) shallonly provide the serving PLMN S-NSSAI part (i.e., the HPLMN S-NSSAI) butno mapped HPLMN S-NSSAI part. When the UE is in roaming condition (i.e.,attached in VPLMN), the network (i.e., VPLMN) shall provide both theserving PLMN S-NSSAI part (i.e., the serving VPLMN S-NSSAI) and themapped HPLMN S-NSSAI part. Therefore, since the S-NSSAI informationelement may comprise the serving PLMN S-NSSAI part and the mapped HPLMNS-NSSAI part in roaming scenario, which S-NSSAI part the UE shouldassociate with the back-off timer should be further defined when theback-off timer is applied in all PLMNs.

Specifically, the UE may be configured to transmit a request message tothe network node. The request message may comprise at least one of a PDUsession establishment request, a PDU session modification request, and aPDU session release request. In an event that the network node is in thecongestion status, the UE may receive a message with a congestion causeand a back-off timer for congestion control from the network node. Themessage may comprise at least one of a PDU session establishment reject,a PDU session modification reject, and a PDU session release command.After receiving the message, the UE may be configured to start theback-off timer. The UE may associate the back-off timer with a mappedHPLMN S-NSSAI in an event that the back-off timer is applied in allPLMN. The UE may determine whether the back-off timer is applied in allPLMN according to an apply back-off timer (ABO) parameter/indicator.

As shown in FIG. 5, the UE may be configured to transmit a PDU sessionestablishment request message to VPLMN 1. The UE may provide a validS-NSSAI value (e.g., S-NSSAI_1) to VPLMN 1. Then, VPLMN 1 may transmit aPDU session establishment accept message to the UE. VPLMN 1 may providethe requested S-NSSAI value (e.g., S-NSSAI_1) to the UE. Thus, the PDUsession may be established between the UE and VPLMN 1 with S-NSSAI_1.

The UE may transmit a PDU session modification request message toVPLM 1. In an event that the network node (e.g., SMF) in VPLMN 1 is inthe congestion status, VPLMN 1 may transmit a PDU session modificationreject message with a congestion cause to the UE. The congestion causemay comprise, for example and without limitation, SGSM cause value #67“insufficient resources for specific slice and DNN” or SGSM cause value#69 “insufficient resources for specific slice”. VPLMN 1 may furtherprovide the ABO parameter/indicator to indicate that the back-off timeris applied in all PLMNs. After receiving the congestion cause and“ABO=applied in all PLMNs”, the UE may be configured to start a back-offtimer. The back-off timer may comprise the congestion back-off timerT3584 or the congestion back-off timer T3585. The UE may associate theback-off timer with the mapped HPLMN S-NSSAI part of S-NSSAI_1.

FIG. 6 illustrates an example scenario 600 under schemes in accordancewith implementations of the present disclosure. Scenario 600 involves aUE and a plurality network nodes, which may be a part of a wirelesscommunication network (e.g., an LTE network, an LTE-Advanced network, a5G/NR network, an IoT network, or a V2X network). Scenario 600illustrates which S-NSSAI value the UE should associate with theback-off timer during the PDU session establishment procedure in anevent that the back-off timer is applied in all PLMNs. The UE may beconfigured to transmit a PDU session establishment request message toVPLMN 1. The UE may provide a valid S-NSSAI value (e.g., S-NSSAI_1) toVPLMN 1. In an event that the network node (e.g., SMF) in VPLMN 1 is inthe congestion status, VPLMN 1 may transmit a PDU session establishmentreject message with a congestion cause to the UE. The congestion causemay comprise, for example and without limitation, 5GSM cause value #67“insufficient resources for specific slice and DNN” or 5GSM cause value#69 “insufficient resources for specific slice”. VPLMN 1 may furtherprovide the ABO parameter/indicator to indicate that the back-off timeris applied in all PLMNs. After receiving the congestion cause and“ABO=applied in all PLMNs”, the UE may be configured to start a back-offtimer. The back-off timer may comprise the congestion back-off timerT3584 or the congestion back-off timer T3585. The UE may associate theback-off timer with the mapped HPLMN S-NSSAI part of S-NSSAI_1.

In accordance with implementations of the present disclosure, it isclearly defined that when the back-off timer is indicated to apply inall PLMNs, it means that the congestion status occurs only in the HPLMN.Therefore, the UE should associate the back-off timer only with themapped HPLMN S-NSSAI part and should not associate the back-off timerwith the serving PLMN S-NSSAI part. In an event that the congestionstatus occurs in the VPLMN, the ABO indicator should be indicated as“the back-off timer is applied in the registered PLMN”. Then, the UEshould associate the back-off timer with the serving PLMN S-NSSAI part.

In some implementations, the UE may provide no S-NSSAI to the networkduring the PDU session establishment procedure. For example, the UE maytransmit a PDU session establishment request message with no S-NSSAI toVPLMN 1. In an event that the network node (e.g., SMF) in VPLMN 1 is inthe congestion status, VPLMN 1 may transmit a reject message with acongestion cause. VPLMN 1 may further provide the parameter/indicatorABO to indicate that the back-off timer is applied in all PLMNs. In anevent that the ABO indicator is indicated as “the back-off timer isapplied in the registered PLMN” and no S-NSSAI is provided by thenetwork node, the UE may associate the back-off timer with no S-NSSAI.In an event that the ABO indicator is indicated as “the back-off timeris applied in all PLMNs” and no S-NSSAI is provided by the network node,the UE may associate the back-off timer with no S-NSSAI.

In some abnormal cases, the UE may be provided with mapped HPLMN S-NSSAIwhen the UE is in non-roaming condition. (i.e., attached in HPLMN). Insuch cases, the UE may register in the HPLMN. The UE may determinewhether the mapped HPLMN S-NSSAI is received from the network node. Inan event that the mapped HPLMN S-NSSAI is received from the networknode, the UE may be configured to associate the back-off timer with themapped HPLMN S-NSSAI or no S-NSSAI after receiving the congestion causeand the ABO indicator is indicated as “the back-off timer is applied inall PLMNs”.

In summary, when the ABO is indicated as “the back-off timer is appliedin all PLMNs”, in the PDU session establishment procedure, in an eventthat the mapped HPLMN S-NSSAI is provided (e.g., both in roaming andnon-roaming scenarios), then the UE may associate the back-off timerwith the mapped HPLMN S-NSSAI only. In an event that the HPLMN S-NSSAIis provided without the mapped HPLMN S-NSSAI (e.g., in non-roamingscenario), then the UE may associate the back-off timer with the HPLMNS-NSSAI. In an event that no-SNSSAI is provided, then the UE mayassociate the back-off timer with no S-NSSAI. In the PDU sessionmodification/release procedure, in an event that the mapped HPLMNS-NSSAI is associated with the PDU session, then the UE may associatethe back-off timer with the mapped HPLMN S-NSSAI only. In an event thatthe HPLMN (e.g., without the mapped HPLMN S-NSSAI) is associated withthe PDU session, then the UE may associate the back-off timer with theHPLMN S-NSSAI. In an event that no-SNSSAI is provided, then the UE mayassociate the back-off timer with no S-NSSAI. When the ABO is indicatedas “the back-off timer is applied in the registered PLMN”, in the PDUestablishment procedure, the UE may associate the back-off timer withthe serving PLMN S-NSSAI only, or both the serving PLMN S-NSSAI and themapped HPLMN S-NSSAI. In an event that no-SNSSAI is provided, then theUE may associate the back-off timer with no S-NSSAI. In the PDU sessionmodification/release procedure, the UE may associate the back-off timerwith the serving PLMN S-NSSAI associated with the PDU session only, orboth the serving PLMN S-NSSAI and the mapped HPLMN S-NSSAI associatedwith the PDU session. The back-off timer may comprise at least one of acongestion back-off timer T3584 and a congestion back-off timer T3585.

FIGS. 7A-7B illustrate an example scenario 700 under schemes inaccordance with implementations of the present disclosure. Scenario 700involves a UE and a plurality network nodes, which may be a part of awireless communication network (e.g., an LTE network, an LTE-Advancednetwork, a 5G/NR network, an IoT network, or a V2X network). Scenario700 illustrates which procedures should be applied with the back-offtimer when the back-off timer is running and applied in all PLMNs.Specifically, the UE may receive a message with a back-off timer fromthe network node. The UE may be configured to start the back-off timerassociated with an S-NSSAI of a PDU session. Then, the UE may determinewhether an S-NSSAI of a request message is the S-NSSAI associated withthe back-off timer. In an event that the S-NSSAI of the request messageis the S-NSSAI associated with the back-off timer, the UE may forbid atransmission of the request message (e.g., the UE is not allowed totransmit the request message). The request message may comprise at leastone of a PDU session establishment request and a PDU sessionmodification request. When the ABO parameter/indicator is indicated as“ABO=applied in all PLMNs” in non-roaming scenario or “ABO=RPLMN”, theS-NSSAI of the request is the S-NSSAI associated with the PDU sessionestablishment request message or the S-NSSAI of the PDU sessionassociated with the PDU session modification request message. When theABO parameter/indicator is indicated as “ABO=applied in all PLMNs” inroaming scenario, the S-NSSAI of the request is the mapped HPLMN S-NSSAIassociated with the PDU session establishment request message or themapped HPLMN S-NSSAI of the PDU session associated with the PDU sessionmodification request message.

As shown in FIGS. 7A-7B, the UE may register in a VPLMN (e.g., roamingscenario) and establish a PDU session with an S-NSSAI (e.g., S-NSSAI_1).The UE may transmit a request message to modify or release the PDUsession. For example, as shown in case 1, the UE may transmit a PDUsession modification request message to the VPLMN. In an event that thenetwork node (e.g., SMF) in the VPLMN is in the congestion status, theVPLMN may transmit a PDU session modification reject message with acongestion cause to the UE. In another example, as shown in case 2, theUE may optionally transmit a PDU session release request message to theVPLM. In an event that the network node (e.g., SMF) in the VPLMN is inthe congestion status, the VPLMN may transmit a PDU session releasecommand message with a congestion cause to the UE. Alternatively, theVPLMN may directly transmit the PDU session release command message tothe UE without receiving the PDU session release request from the UE.Then, the UE may transmit a PDU session release complete message to theVPLMN. The congestion cause may comprise, for example and withoutlimitation, 5GSM cause value #67 “insufficient resources for specificslice and DNN” or 5GSM cause value #69 “insufficient resources forspecific slice”. The VPLMN may further provide the ABOparameter/indicator to indicate that the back-off timer is applied inall PLMNs. After receiving the congestion cause and “ABO=applied in allPLMNs”, the UE may be configured to start a back-off timer. The back-offtimer may comprise the congestion back-off timer T3584 or the congestionback-off timer T3585. The UE may associate the back-off timer with themapped HPLMN S-NSSAI part of S-NSSAI_1.

When the back-off timer is running, the UE is under congestion controland forbidden to send a request message that the associated S-NSSAI isidentical to the S-NSSAI associated with the back-off timer. The UE maybe configured to compare the S-NSSAI associated with the back-off timerwith the S-NSSAI associated with the request message. For example, theUE is not allowed to send a PDU session establishment request when themapped HPLMN S-NSSAI part of S-NSSAI_1 associated with the back-offtimer is the same as the mapped HPLMN S-NSSAI part of the S-NSSAI of thePDU session establishment request. In another example, the UE is notallowed to send a PDU session modification request when the mapped HPLMNS-NSSAI part of S-NSSAI_1 associated with the back-off timer is the sameas the mapped HPLMN S-NSSAI part of the S-NSSAI of the PDU session(e.g., the current/latest PDU session).

When the back-off timer is running, the UE may move to a different PLMN(e.g., inter-PLMN change). For example, the UE may transfer from theVPLMN to the HPLMN (e.g., non-roaming scenario). At this time, theS-NSSAI of the PDU session may also be updated from S-NSSAI_1 toS-NSSAI_2 where S-NSSAI_2 is the mapped HPLMN S-NSSAI part of S-NSSAI_1.The PDU session now may be associated to S-NSSAI_2. S-NSSAI_2 may be theserving PLMN S-NSSAI or the mapped HPLMN S-NSSAI provided by the networknode. The UE may apply the back-off timer to S-NSSAI_2 since theback-off timer is applied in all PLMNs. Since the UE is still undercongestion control and the S-NSSAI of the current/latest PDU session ischanged, the UE is forbidden to send a request message that theassociated S-NSSAI of the current/latest PDU session is identical to theS-NSSAI associated with the back-off timer. The UE may be configured tocompare the S-NSSAI associated with the back-off timer with the S-NSSAIassociated with the request message of the current/latest PDU session.For example, the UE is not allowed to send a PDU session establishmentrequest when S-NSSAI_2 associated with the back-off timer is the same asthe S-NSSAI (e.g., serving PLMN S-NSSAI or mapped HPLMN S-NSSAI) of thePDU session establishment request. In another example, the UE is notallowed to send a PDU session modification request when S-NSSAI_2associated with the back-off timer is the same as the S-NSSAI (e.g.,serving PLMN S-NSSAI or mapped HPLMN S-NSSAI) of the PDU session (e.g.,the current/latest PDU session).

In another example, when the back-off timer is running, the UE maytransfer from a first VPLMN (e.g., VPLMN_1) to a second VPLMN (e.g.,VPLMN_2) during the inter-PLMN change (e.g., still in roaming scenario).At this time, the S-NSSAI of the PDU session may also be updated from afirst S-NSSAI (e.g., S-NSSAI_1) to a second S-NSSAI (e.g., S-NSSAI_2).The PDU session now may be associated to S-NSSAI_2. The UE may now applythe back-off timer to the mapped HPLMN S-NSSAI of S-NSSAI_2 since theback-off timer is applied in all PLMNs. Since the UE is still undercongestion control and the S-NSSAI of the current/latest PDU session ischanged, the UE is forbidden to send a request message that theassociated mapped HPLMN S-NSSAI of the current/latest PDU session (e.g.,mapped HPLMN S-NSSAI of S-NSSAI_2) is identical to the S-NSSAIassociated with the back-off timer. The UE may be configured to comparethe S-NSSAI associated with the back-off timer with the mapped HPLMNS-NSSAI associated with the request message of the current/latest PDUsession. For example, the UE is not allowed to send a PDU sessionestablishment request when the S-NSSAI associated with the back-offtimer is the same as the mapped HPLMN S-NSSAI part of the PDU sessionestablishment request. In another example, the UE is not allowed to senda PDU session modification request when the S-NSSAI associated with theback-off timer is the same as the mapped HPLMN S-NSSAI part of the PDUsession (e.g., the current/latest PDU session).

FIGS. 8A-8B illustrate an example scenario 800 under schemes inaccordance with implementations of the present disclosure. Scenario 800involves a UE and a plurality network nodes, which may be a part of awireless communication network (e.g., an LTE network, an LTE-Advancednetwork, a 5G/NR network, an IoT network, or a V2X network). Scenario800 illustrates which procedures should be applied with the back-offtimer when the back-off timer is running and applied in the RPLMN. Asshown in FIGS. 8A-8B, the UE may register in a VPLMN (e.g., roamingscenario) and establish a PDU session with an S-NSSAI (e.g., S-NSSAI_1).The UE may transmit a request message to modify or release the PDUsession. For example, as shown in case 1, the UE may transmit a PDUsession modification request message to the VPLMN. In an event that thenetwork node (e.g., SMF) in the VPLMN is in the congestion status, theVPLMN may transmit a PDU session modification reject message with acongestion cause to the UE. In another example, as shown in case 2, theUE may optionally transmit a PDU session release request message to theVPLM. In an event that the network node (e.g., SMF) in the VPLMN is inthe congestion status, the VPLMN may transmit a PDU session releasecommand message with a congestion cause to the UE. Alternatively, theVPLMN may directly transmit the PDU session release command message tothe UE without receiving the PDU session release request from the UE.Then, the UE may transmit a PDU session release complete message to theVPLMN. The congestion cause may comprise, for example and withoutlimitation, 5GSM cause value #67 “insufficient resources for specificslice and DNN” or 5GSM cause value #69 “insufficient resources forspecific slice”. The VPLMN may further provide the ABOparameter/indicator to indicate that the back-off timer is applied inthe RPLMN. After receiving the congestion cause and “ABO=applied in theRPLMN”, the UE may be configured to start a back-off timer. The back-offtimer may comprise the congestion back-off timer T3584 or the congestionback-off timer T3585. The UE may associate the back-off timer withS-NSSAI_1.

When the back-off timer is running, the UE is under congestion controland forbidden to send a request message that the associated S-NSSAI isidentical to the S-NSSAI associated with the back-off timer. The UE maybe configured to compare the S-NSSAI associated with the back-off timerwith the S-NSSAI associated with the request message. For example, theUE is not allowed to send a PDU session establishment request whenS-NSSAI_1 associated with the back-off timer is the same as the S-NSSAIof the PDU session establishment request. In another example, the UE isnot allowed to send a PDU session modification request when S-NSSAI_1associated with the back-off timer is the same as the S-NSSAI of the PDUsession (e.g., the current/latest PDU session).

When the back-off timer is running, the UE may move to a different PLMN(e.g., inter-PLMN change). For example, the UE may transfer from theVPLMN to the HPLMN (e.g., non-roaming scenario). At this time, theS-NSSAI of the PDU session may also be updated from S-NSSAI_1 toS-NSSAI_2 where S-NSSAI_2 is the mapped HPLMN S-NSSAI part of S-NSSAI_1.The PDU session now may be associated to S-NSSAI_2. S-NSSAI_2 may be theserving PLMN S-NSSAI or the mapped HPLMN S-NSSAI provided by the networknode. The UE may be configured not to apply the back-off timer toS-NSSAI_2 (i.e., HPLMN) since the back-off timer is only applicable inthe VPLMN (i.e., ABO=ABO=applied in the RPLMN). The back-off timerassociated with S-NSSAI_1 is not applicable in the HPLMN. The UE isallowed to send a request message that the associated S-NSSAI of thecurrent/latest PDU session is not identical to the S-NSSAI associatedwith the back-off timer. The UE may be configured to compare the S-NSSAIassociated with the back-off timer with the S-NSSAI associated with therequest message of the current/latest PDU session. For example, the UEis able to send a PDU session establishment request since S-NSSAI_1associated with the back-off timer is not the same as the S-NSSAI (e.g.,serving PLMN S-NSSAI or mapped HPLMN S-NSSAI) of the PDU sessionestablishment request. In another example, the UE is able to send a PDUsession modification request since S-NSSAI_1 associated with theback-off timer is not the same as the S-NSSAI (e.g., serving PLMNS-NSSAI or mapped HPLMN S-NSSAI) of the PDU session (e.g., thecurrent/latest PDU session).

In summary, in the PDU session establishment or modification procedure,when the ABO is indicated as “the back-off timer is applied in allPLMNs” and the UE is in the roaming scenario, the UE is forbidden tosend a request message in an event that the mapped HPLMN S-NSSAI of therequest message is the same as the mapped HPLMN S-NSSAI associated withthe back-off timer. When the ABO is indicated as “the back-off timer isapplied in all PLMNs” and the UE is in the non-roaming scenario, the UEis forbidden to send a request message in an event that the mapped HPLMNS-NSSAI or serving PLMN S-NSSAI of the request message is the same asthe mapped HPLMN S-NSSAI associated with the back-off timer. When theABO is indicated as “the back-off timer is applied the RPLMN”, the UE isforbidden to send a request message in an event that the S-NSSAI or theserving PLMN S-NSSAI of the request message is the same as the S-NSSAIassociated with the back-off timer. The back-off timer is not applicablein an event that the UE performs inter-PLMN change from the VPLMN toHPLMN.

Accordingly, when a back-off is configured, the UE can use the S-NSSAIof the current/latest PDU session rather than the S-NSSAI of the old PDUsession to compare with the S-NSSAI associated with the back-off timerto determine whether it is forbidden to send the request message. Thus,the UE can apply the back-off timer to the appropriate procedures andcan fulfill the congestion control initiated by the network node.

FIG. 9 illustrates an example scenario 900 under schemes in accordancewith implementations of the present disclosure. Scenario 900 involves aUE and a plurality network nodes, which may be a part of a wirelesscommunication network (e.g., an LTE network, an LTE-Advanced network, a5G/NR network, an IoT network, or a V2X network). Scenario 900illustrates how to stop the back-off timer when the back-off timer isrunning. Specifically, the UE may receive a message with a back-offtimer from the network node. The UE may be configured to start theback-off timer associated with an S-NSSAI of a PDU session. When theback-off timer is running, the UE may further receive a 5GSM messagefrom the network node. Then, the UE may determine whether an S-NSSAI ofPDU session of the 5GSM message is the S-NSSAI associated with theback-off timer. In an event that the S-NSSAI of PDU session of the 5GSMmessage is the S-NSSAI associated with the back-off timer, the UE may beconfigured to stop the back-off timer. The 5GSM message may comprise atleast one of a PDU session modification command and a PDU sessionrelease command without a back-off timer value information element.

As shown in FIG. 9, the UE may register in a VPLMN (e.g., roamingscenario) and establish a PDU session with an S-NSSAI (e.g., S-NSSAI_1).When the back-off timer is running, the UE may further receive a 5GSMmessage from the network node. For example, as shown in case 1, the UEmay receive a PDU session modification command message from the VPLMN.Then, the UE may transmit a PDU session modification complete message tothe VPLMN. In another example, as shown in case 2, the UE may optionallytransmit a PDU session release request message to the VPLM. The VPLMNmay transmit a PDU session release command message without the back-offtimer information element to the UE. Alternatively, the VPLMN maydirectly transmit the PDU session release command message to the UEwithout receiving the PDU session release request from the UE. Then, theUE may transmit a PDU session release complete message to the VPLMN.

The VPLMN may further provide the ABO parameter/indicator to indicatethat the back-off timer is applied in all PLMNs. After receiving thecongestion cause and “ABO=applied in all PLMNs”, the UE may beconfigured to start a back-off timer. The back-off timer may comprisethe congestion back-off timer T3584 or the congestion back-off timerT3585. The UE may associate the back-off timer with the mapped HPLMNS-NSSAI part of S-NSSAI_1. In case of a roaming scenario, afterreceiving the 5GSM message, the UE may be configured to determinewhether a mapped HPLMN S-NSSAI of PDU session of the 5GSM message is thesame as the mapped HPLMN S-NSSAI part of S-NSSAI_1 associated with theback-off timer. In an event that the result is yes, the UE may beconfigured to stop the back-off timer. In case of a non-roamingscenario, the UE may be configured to determine whether a mapped HPLMNS-NSSAI or serving PLMN S-NSSAI of PDU session of the 5GSM message isthe same as the mapped HPLMN S-NSSAI part of S-NSSAI_1 associated withthe back-off timer. In an event that the result is yes, the UE may beconfigured to stop the back-off timer.

Alternatively, after receiving the congestion cause and “ABO=applied inthe RPLMN”, the UE may be configured to start a back-off timer. Theback-off timer may comprise the congestion back-off timer T3584 or thecongestion back-off timer T3585. The UE may associate the back-off timerwith S-NSSAI_1. After receiving the 5GSM message, the UE may beconfigured to determine whether the serving PLMN S-NSSAI of PDU sessionof the 5GSM message is the same as S-NSSAI_1 associated with theback-off timer. In an event that the result is yes, the UE may beconfigured to stop the back-off timer.

In summary, after receiving the PDU session modification command or thePDU session release command without a back-off timer value informationelement, when the ABO is indicated as “the back-off timer is applied inall PLMNs” and the UE is in the roaming scenario, the UE may stop theback-off timer in an event that the mapped HPLMN S-NSSAI of PDU sessionof the 5GSM message is the same as the mapped HPLMN S-NSSAI associatedwith the back-off timer. When the ABO is indicated as “the back-offtimer is applied in all PLMNs” and the UE is in the non-roamingscenario, the UE may stop the back-off timer in an event that the mappedHPLMN S-NSSAI or serving PLMN S-NSSAI of PDU session of the 5GSM messageis the same as the mapped HPLMN S-NSSAI associated with the back-offtimer. When the ABO is indicated as “the back-off timer is applied theRPLMN”, the UE may stop the back-off timer in an event that the S-NSSAIor the serving PLMN S-NSSAI of PDU session of the 5GSM message is thesame as the S-NSSAI associated with the back-off timer.

Accordingly, when a back-off is running, the UE can use the S-NSSAI ofPDU session of the 5GSM message rather than the S-NSSAI of the old PDUsession to compare with the S-NSSAI associated with the back-off timerto determine whether it can stop the back-off timer. Thus, the UE canstop the back-off timer appropriately while fulfilling the congestioncontrol initiated by the network node.

Illustrative Implementations

FIG. 10 illustrates an example communication apparatus 1010 and anexample network apparatus 1020 in accordance with an implementation ofthe present disclosure. Each of communication apparatus 1010 and networkapparatus 1020 may perform various functions to implement schemes,techniques, processes and methods described herein pertaining to S-NSSAIbased congestion control enhancement with respect to user equipment andnetwork apparatus in wireless communications, includingschemes/scenarios described above as well as processes 1100, 1200, 1300and 1400 described below.

Communication apparatus 1010 may be a part of an electronic apparatus,which may be a UE such as a portable or mobile apparatus, a wearableapparatus, a wireless communication apparatus or a computing apparatus.For instance, communication apparatus 1010 may be implemented in asmartphone, a smartwatch, a personal digital assistant, a digitalcamera, or a computing equipment such as a tablet computer, a laptopcomputer, a notebook computer or a vehicle. Communication apparatus 1010may also be a part of a machine type apparatus, which may be an IoT,NB-IoT, or IIoT apparatus such as an immobile or a stationary apparatus,a home apparatus, a wire communication apparatus or a computingapparatus. Alternatively, communication apparatus 1010 may beimplemented in the form of one or more integrated-circuit (IC) chipssuch as, for example and without limitation, one or more single-coreprocessors, one or more multi-core processors, one or morereduced-instruction set computing (RISC) processors, or one or morecomplex-instruction-set-computing (CISC) processors. Communicationapparatus 1010 may include at least some of those components shown inFIG. 10 such as a processor 1012, for example. Processor 1012 mayfurther comprise protocol stacks and a set of system modules andcircuits which may be implemented and configured by software, firmware,hardware, and/or combination thereof. The function modules and circuits,when executed by the processors via program instructions contained inmemory 1014, interwork with each other to allow communication apparatus1010 to perform embodiments and functional tasks and features in thenetwork. For example, system modules and circuits may comprise a PDUsession handling circuit that performs PDU session establishment andmodification procedures with network apparatus 1020, a policy controlcircuit that performs URSP rule matching, and a configuration andcontrol circuit that handles configuration and control parameters formobility management and session management. Communication apparatus 1010may further include one or more other components not pertinent to theproposed scheme of the present disclosure (e.g., internal power supply,display device and/or user interface device), and, thus, suchcomponent(s) of communication apparatus 1010 are neither shown in FIG.10 nor described below in the interest of simplicity and brevity.

Network apparatus 1020 may be a part of an electronic apparatus, whichmay be a network node such as a base station, a small cell, a router ora gateway. For instance, network apparatus 1020 may be implemented in aneNodeB in an LTE, LTE-Advanced or LTE-Advanced Pro network or in a gNBin a 5G, NR, IoT, NB-IoT, IIoT or V2X network. Alternatively, networkapparatus 1020 may be implemented in the form of one or more IC chipssuch as, for example and without limitation, one or more single-coreprocessors, one or more multi-core processors, or one or more RISC orCISC processors. Network apparatus 1020 may include at least some ofthose components shown in FIG. 10 such as a processor 1022, for example.Processor 1022 may further include protocol stacks and a set of controlfunctional modules and circuit. For example, a PDU session handlingcircuit may handle PDU session establishment and modificationprocedures. A policy control circuit may configure policy rules forcommunication apparatus 1010. A configuration and control circuit mayprovide different parameters to configure and control communicationapparatus 1010 of related functionalities including mobility managementand session management. Network apparatus 1020 may further include oneor more other components not pertinent to the proposed scheme of thepresent disclosure (e.g., internal power supply, display device and/oruser interface device), and, thus, such component(s) of networkapparatus 1020 are neither shown in FIG. 10 nor described below in theinterest of simplicity and brevity.

In one aspect, each of processor 1012 and processor 1022 may beimplemented in the form of one or more single-core processors, one ormore multi-core processors, or one or more CISC processors. That is,even though a singular term “a processor” is used herein to refer toprocessor 1012 and processor 1022, each of processor 1012 and processor1022 may include multiple processors in some implementations and asingle processor in other implementations in accordance with the presentdisclosure. In another aspect, each of processor 1012 and processor 1022may be implemented in the form of hardware (and, optionally, firmware)with electronic components including, for example and withoutlimitation, one or more transistors, one or more diodes, one or morecapacitors, one or more resistors, one or more inductors, one or morememristors and/or one or more varactors that are configured and arrangedto achieve specific purposes in accordance with the present disclosure.In other words, in at least some implementations, each of processor 1012and processor 1022 is a special-purpose machine specifically designed,arranged and configured to perform specific tasks in a device (e.g., asrepresented by communication apparatus 1010) and a network (e.g., asrepresented by network apparatus 1020) in accordance with variousimplementations of the present disclosure.

In some implementations, communication apparatus 1010 may also include atransceiver 1016 coupled to processor 1012 and capable of wirelesslytransmitting and receiving data. In some implementations, communicationapparatus 1010 may further include a memory 1014 coupled to processor1012 and capable of being accessed by processor 1012 and storing datatherein. In some implementations, network apparatus 1020 may alsoinclude a transceiver 1026 coupled to processor 1022 and capable ofwirelessly transmitting and receiving data. In some implementations,network apparatus 1020 may further include a memory 1024 coupled toprocessor 1022 and capable of being accessed by processor 1022 andstoring data therein. Accordingly, communication apparatus 1010 andnetwork apparatus 1020 may wirelessly communicate with each other viatransceiver 1016 and transceiver 1026, respectively. To aid betterunderstanding, the following description of the operations,functionalities and capabilities of each of communication apparatus 1010and network apparatus 1020 is provided in the context of a mobilecommunication environment in which communication apparatus 1010 isimplemented in or as a communication apparatus or a UE and networkapparatus 1020 is implemented in or as a network node of a communicationnetwork.

In some implementations, processor 1012 may be configured to transmit,via transceiver 1016, a request message to network apparatus 1020. Therequest message may comprise at least one of a PDU session establishmentrequest, a PDU session modification request, and a PDU session releaserequest. In an event that network apparatus 1020 is in the congestionstatus, processor 1012 may receive, via transceiver 1016, a message witha congestion cause and a back-off timer for congestion control fromnetwork apparatus 1020. The message may comprise at least one of a PDUsession establishment reject, a PDU session modification reject, and aPDU session release command. After receiving the message, processor 1012may be configured to start a back-off timer. Processor 1012 mayassociate the back-off timer with an S-NSSAI in an event that theS-NSSAI is provided by network apparatus 1020. The S-NSSAI is theupdated/latest S-NSSAI of the current PDU session provided by networkapparatus 1020. The back-off timer started by processor 1012 maycomprise at least one of a congestion back-off timer T3584 and acongestion back-off timer T3585.

In some implementations, processor 1012 may register in a first PLMN(e.g., VPLMN 1). Processor 1012 may be configured to transmit, viatransceiver 1016, a PDU session establishment request message toVPLMN 1. Processor 1012 may provide no S-NSSAI to VPLMN 1 (e.g.,processor 1012 does not provide any S-NSSAI value). Then, VPLMN 1 maytransmit a PDU session establishment accept message to processor 1012.VPLMN 1 may select and provide an S-NSSAI value (e.g., S-NSSAI_1) toprocessor 1012. Thus, the PDU session may be established betweencommunication apparatus 1010 and VPLMN 1 with S-NSSAI_1. Processor 1012may transfer from the first PLMN to a second PLMN (e.g., inter-PLMNchange from VPLMN 1 to VPLMN 2). The S-NSSAI of the PDU session may bechanged from S-NSSAI_1 to S-NSSAI_2. At this moment, the PDU session maybe maintained between communication apparatus 1010 and VPLMN 2 withS-NSSAI_2. When in the VPLMN 2, processor 1012 may be configured toperform a PDU session modification/release procedure with VPLMN 2. VPLMN2 may transmit a message with a congestion cause. After receiving thecongestion cause, processor 1012 may be configured to start a back-offtimer. The back-off timer may comprise the congestion back-off timerT3584 or the congestion back-off timer T3585. Processor 1012 mayassociate the back-off timer with the updated/latest S-NSSAI (e.g.,S-NSSAI_2).

In some implementations, processor 1012 may be configured to transmit,via transceiver 1016, a request message to network apparatus 1020. Therequest message may comprise at least one of a PDU session establishmentrequest, a PDU session modification request, and a PDU session releaserequest. In an event that network apparatus 1020 is in the congestionstatus, processor 1012 may receive a message with a congestion cause anda back-off timer for congestion control from the network node. Themessage may comprise at least one of a PDU session establishment reject,a PDU session modification reject, and a PDU session release command.After receiving the message, processor 1012 may be configured to startthe back-off timer. Processor 1012 may associate the back-off timer witha mapped HPLMN S-NSSAI in an event that the back-off timer is applied inall PLMN. Processor 1012 may determine whether the back-off timer isapplied in all PLMN according to an ABO parameter/indicator.

In some implementations, processor 1012 may be configured to transmit,via transceiver 1016, a PDU session establishment request message tonetwork apparatus 1020. Processor 1012 may provide a valid S-NSSAI value(e.g., S-NSSAI_1) to network apparatus 1020. In an event that one thenetwork node (e.g., SMF) is in the congestion status, processor 1022 maytransmit, via transceiver 1026, a PDU session establishment rejectmessage with a congestion cause to communication apparatus 1010.Processor 1022 may further provide the ABO parameter/indicator toindicate that the back-off timer is applied in all PLMNs. Afterreceiving the congestion cause and “ABO=applied in all PLMNs”, processor1012 may be configured to start a back-off timer. The back-off timer maycomprise the congestion back-off timer T3584 or the congestion back-offtimer T3585. Processor 1012 may associate the back-off timer with themapped HPLMN S-NSSAI part of S-NSSAI_1.

In some implementations, processor 1012 may receive, via transceiver1016, a message with a back-off timer from network apparatus 1020.Processor 1012 may be configured to start the back-off timer associatedwith an S-NSSAI of a PDU session. Then, processor 1012 may determinewhether an S-NSSAI of a request message is the S-NSSAI associated withthe back-off timer. In an event that the S-NSSAI of the request messageis the S-NSSAI associated with the back-off timer, processor 1012 mayforbid a transmission of the request message (e.g., processor 1012 isnot allowed to transmit the request message). The request message maycomprise at least one of a PDU session establishment request and a PDUsession modification request.

In some implementations, processor 1012 may receive, via transceiver1016, a message with a back-off timer from the network node. Processor1012 may be configured to start the back-off timer associated with anS-NSSAI of a PDU session. When the back-off timer is running, processor1012 may further receive a 5GSM message from network apparatus 1020.Then, processor 1012 may determine whether an S-NSSAI of PDU session ofthe 5GSM message is the S-NSSAI associated with the back-off timer. Inan event that the S-NSSAI of PDU session of the 5GSM message is theS-NSSAI associated with the back-off timer, processor 1012 may beconfigured to stop the back-off timer. The 5GSM message may comprise atleast one of a PDU session modification command and a PDU sessionrelease command without a back-off timer value information element.

Illustrative Processes

FIG. 11 illustrates an example process 1100 in accordance with animplementation of the present disclosure. Process 1100 may be an exampleimplementation of above scenarios/schemes, whether partially orcompletely, with respect to applying the updated/latest S-NSSAI of thePDU session to the back-off timer for the S-NSSAI based congestioncontrol with the present disclosure. Process 1100 may represent anaspect of implementation of features of communication apparatus 1010.Process 1100 may include one or more operations, actions, or functionsas illustrated by one or more of blocks 1110, 1120, 1130 and 1140.Although illustrated as discrete blocks, various blocks of process 1100may be divided into additional blocks, combined into fewer blocks, oreliminated, depending on the desired implementation. Moreover, theblocks of process 1100 may executed in the order shown in FIG. 11 or,alternatively, in a different order. Process 1100 may be implemented bycommunication apparatus 1010, any suitable UE or machine type devices.Solely for illustrative purposes and without limitation, process 1100 isdescribed below in the context of n communication apparatus 1010.Process 1100 may begin at block 1110.

At 1110, process 1100 may involve processor 1012 of apparatus 1010receiving a message with a back-off timer from a network node. Process1100 may proceed from 1110 to 1120.

At 1120, process 1100 may involve processor 1012 determining whether anS-NSSAI of a PDU session is provided by the network node. Process 1100may proceed from 1120 to 1130.

At 1130, process 1100 may involve processor 1012 starting the back-offtimer. Process 1100 may proceed from 1130 to 1140.

At 1140, process 1100 may involve processor 1012 associating theback-off timer with the S-NSSAI of the PDU session in an event that theS-NSSAI is provided by the network node.

In some implementations, process 1100 may involve processor 1012transmitting a request message to the network node. The request messagemay comprise at least one of a PDU session establishment request, a PDUsession modification request, and a PDU session release request.

In some implementations, the message may comprise at least one of a PDUsession establishment reject, a PDU session modification reject, and aPDU session release command.

In some implementations, the S-NSSAI may be a current or latest S-NSSAIof the PDU session.

In some implementations, process 1100 may involve processor 1012transmitting a PDU session establishment request message with a validS-NSSAI or no S-NSSAI to the network node.

In some implementations, process 1100 may involve processor 1012transferring from a first public land mobile network (PLMN) to a secondPLMN. Process 1100 may further involve processor 1012 receiving theS-NSSAI associated with the second PLMN from the network node.

In some implementations, the message may comprises a 5GSM cause value#67 which represents insufficient resources for a specific slice and DNNor a 5GSM cause value #69 which represents insufficient resources for aspecific slice.

In some implementations, the back-off timer may comprise at least one ofa congestion back-off timer T3584 and a congestion back-off timer T3585.

FIG. 12 illustrates an example process 1200 in accordance with animplementation of the present disclosure. Process 1200 may be an exampleimplementation of above scenarios/schemes, whether partially orcompletely, with respect to how to associate the S-NSSAI value with theback-off timer in an event that the back-off timer is applied in allPLMNs with the present disclosure. Process 1200 may represent an aspectof implementation of features of communication apparatus 1010. Process1200 may include one or more operations, actions, or functions asillustrated by one or more of blocks 1210, 1220, 1230 and 1240. Althoughillustrated as discrete blocks, various blocks of process 1200 may bedivided into additional blocks, combined into fewer blocks, oreliminated, depending on the desired implementation. Moreover, theblocks of process 1200 may executed in the order shown in FIG. 12 or,alternatively, in a different order. Process 1200 may be implemented bycommunication apparatus 1010, any suitable UE or machine type devices.Solely for illustrative purposes and without limitation, process 1200 isdescribed below in the context of n communication apparatus 1010.Process 1200 may begin at block 1210.

At 1210, process 1200 may involve processor 1012 of apparatus 1010receiving a message with a back-off timer from a network node. Process1200 may proceed from 1210 to 1220.

At 1220, process 1200 may involve processor 1012 determining whether theback-off timer is applied in all PLMNs. Process 1200 may proceed from1220 to 1230.

At 1230, process 1200 may involve processor 1012 starting the back-offtimer. Process 1200 may proceed from 1230 to 1240.

At 1240, process 1200 may involve processor 1012 associating theback-off timer with a mapped HPLMN S-NSSAI of a PDU session in an eventthat the back-off timer is applied in all PLMNs.

In some implementations, process 1200 may involve processor 1012transmitting a request message to the network node. The request messagemay comprise at least one of a PDU session establishment request, a PDUsession modification request, and a PDU session release request.

In some implementations, the message may comprise at least one of a PDUsession establishment reject, a PDU session modification reject, and aPDU session release command.

In some implementations, process 1200 may involve processor 1012determining whether the back-off timer is applied in all PLMNs accordingto an ABO parameter.

In some implementations, process 1200 may involve processor 1012transmitting a PDU session establishment request message with a validS-NSSAI to the network node.

In some implementations, process 1200 may involve processor 1012transmitting a PDU session establishment request message with no S-NSSAIto the network node.

In some implementations, process 1200 may involve processor 1012registering in a VPLMN. The back-off timer may be not associated with aserving PLMN S-NSSAI but associated with the mapped HPLMN S-NSSAI.

In some implementations, the message may comprise a 5GSM cause value #67which represents insufficient resources for a specific slice and DNN ora 5GSM cause value #69 which represents insufficient resources for aspecific slice.

In some implementations, process 1200 may involve processor 1012registering in an HPLMN. Process 1200 may also involve processor 1012determining whether the mapped HPLMN S-NSSAI is received from thenetwork node. Process 1200 may further involve processor 1012associating the back-off timer with the mapped HPLMN S-NSSAI in an eventthat the mapped HPLMN S-NSSAI is received from the network node.

In some implementations, the back-off timer may comprise at least one ofa congestion back-off timer T3584 and a congestion back-off timer T3585.

FIG. 13 illustrates an example process 1300 in accordance with animplementation of the present disclosure. Process 1300 may be an exampleimplementation of above scenarios/schemes, whether partially orcompletely, with respect to which procedures should be applied with theback-off timer when the back-off timer is running and applied in allPLMNs with the present disclosure. Process 1300 may represent an aspectof implementation of features of communication apparatus 1010. Process1300 may include one or more operations, actions, or functions asillustrated by one or more of blocks 1310, 1320, 1330 and 1340. Althoughillustrated as discrete blocks, various blocks of process 1300 may bedivided into additional blocks, combined into fewer blocks, oreliminated, depending on the desired implementation. Moreover, theblocks of process 1300 may executed in the order shown in FIG. 13 or,alternatively, in a different order. Process 1300 may be implemented bycommunication apparatus 1010, any suitable UE or machine type devices.Solely for illustrative purposes and without limitation, process 1300 isdescribed below in the context of n communication apparatus 1010.Process 1300 may begin at block 1310.

At 1310, process 1300 may involve processor 1012 of apparatus 1010receiving a message with a back-off timer from a network node. Process1300 may proceed from 1310 to 1320.

At 1320, process 1300 may involve processor 1012 starting the back-offtimer associated with an S-NSSAI of a PDU session. Process 1300 mayproceed from 1320 to 1330.

At 1330, process 1300 may involve processor 1012 determining whether anS-NSSAI of a request message is the S-NSSAI associated with the back-offtimer. Process 1300 may proceed from 1330 to 1340.

At 1340, process 1300 may involve processor 1012 forbidding atransmission of the request message in an event that the S-NSSAI of therequest message is the S-NSSAI associated with the back-off timer.

In some implementations, the request message may comprise at least oneof a PDU session establishment request and a PDU session modificationrequest.

In some implementations, the S-NSSAI of the request may be the S-NSSAIassociated with the PDU session establishment request message, or theS-NSSAI of the PDU session associated with the PDU session modificationrequest message.

In some implementations, the S-NSSAI of the request may the mapped HPLMNS-NSSAI associated with the PDU session establishment request message,or the mapped HPLMN S-NSSAI of the PDU session associated with the PDUsession modification request message.

In some implementations, when the back-off timer is applied in allPLMNs, the S-NSSAI of the request message may comprise a mapped HPLMNS-NSSAI of the PDU session or a mapped HPLMN S-NSSAI of the PDU sessionestablishment request. The S-NSSAI associated with the back-off timermay comprise a mapped HPLMN S-NSSAI.

In some implementations, when the back-off timer is applied in allPLMNs, the S-NSSAI of the request message may comprise an HPLMN S-NSSAIor serving PLMN S-NSSAI of the PDU session or an HPLMN S-NSSAI orserving PLMN S-NSSAI of the PDU session establishment request. TheS-NSSAI associated with the back-off timer may comprise a mapped HPLMNS-NSSAI.

In some implementations, when the back-off timer is applied in an RPLMN,the S-NSSAI of the request message may comprise an S-NSSAI of the PDUsession or an S-NSSAI of the PDU session establishment request.

FIG. 14 illustrates an example process 1400 in accordance with animplementation of the present disclosure. Process 1400 may be an exampleimplementation of above scenarios/schemes, whether partially orcompletely, with respect to how to stop the back-off timer when theback-off timer is running with the present disclosure. Process 1400 mayrepresent an aspect of implementation of features of communicationapparatus 1010. Process 1400 may include one or more operations,actions, or functions as illustrated by one or more of blocks 1410,1420, 1430, 1440 and 1450. Although illustrated as discrete blocks,various blocks of process 1400 may be divided into additional blocks,combined into fewer blocks, or eliminated, depending on the desiredimplementation. Moreover, the blocks of process 1400 may executed in theorder shown in FIG. 14 or, alternatively, in a different order. Process1400 may be implemented by communication apparatus 1010, any suitable UEor machine type devices. Solely for illustrative purposes and withoutlimitation, process 1400 is described below in the context of ncommunication apparatus 1010. Process 1400 may begin at block 1410.

At 1410, process 1400 may involve processor 1012 of apparatus 1010receiving a message with a back-off timer from a network node. Process1400 may proceed from 1410 to 1420.

At 1420, process 1400 may involve processor 1012 starting the back-offtimer associated with an S-NSSAI of a PDU session. Process 1400 mayproceed from 1420 to 1430.

At 1430, process 1400 may involve processor 1012 receiving a SGSMmessage from the network node. Process 1400 may proceed from 1430 to1440.

At 1440, process 1400 may involve processor 1012 determining whether anS-NSSAI of PDU session of the 5GSM message is the S-NSSAI associatedwith the back-off timer. Process 1400 may proceed from 1440 to 1440.

At 1450, process 1400 may involve processor 1012 stopping the back-offtimer in an event that the S-NSSAI of PDU session of the 5GSM message isthe S-NSSAI associated with the back-off timer.

In some implementations, the 5GSM message may comprise at least one of aPDU session modification command and a PDU session release commandwithout a back-off timer value information element.

In some implementations, when the back-off timer is applied in allPLMNs, the S-NSSAI of PDU session of the 5GSM message may comprise amapped HPLMN S-NSSAI of PDU session of the 5GSM message. The S-NSSAIassociated with the back-off timer may comprise a mapped HPLMN S-NSSAI.

In some implementations, when the back-off timer is applied in allPLMNs, the S-NSSAI of PDU session of the 5GSM message may comprise amapped HPLMN S-NSSAI or serving PLMN S-NSSAI of PDU session of the 5GSMmessage. The S-NSSAI associated with the back-off timer may comprise amapped HPLMN S-NSSAI.

In some implementations, when the back-off timer is applied in an RPLMN,the S-NSSAI of PDU session of the 5GSM message may comprise a servingPLMN S-NSSAI of PDU session of the 5GSM message.

Additional Notes

The herein-described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely examples, and that in fact many other architectures can beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected”, or“operably coupled”, to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable”, to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

Further, with respect to the use of substantially any plural and/orsingular terms herein, those having skill in the art can translate fromthe plural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

Moreover, it will be understood by those skilled in the art that, ingeneral, terms used herein, and especially in the appended claims, e.g.,bodies of the appended claims, are generally intended as “open” terms,e.g., the term “including” should be interpreted as “including but notlimited to,” the term “having” should be interpreted as “having atleast,” the term “includes” should be interpreted as “includes but isnot limited to,” etc. It will be further understood by those within theart that if a specific number of an introduced claim recitation isintended, such an intent will be explicitly recited in the claim, and inthe absence of such recitation no such intent is present. For example,as an aid to understanding, the following appended claims may containusage of the introductory phrases “at least one” and “one or more” tointroduce claim recitations. However, the use of such phrases should notbe construed to imply that the introduction of a claim recitation by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim recitation to implementations containing only onesuch recitation, even when the same claim includes the introductoryphrases “one or more” or “at least one” and indefinite articles such as“a” or “an,” e.g., “a” and/or “an” should be interpreted to mean “atleast one” or “one or more;” the same holds true for the use of definitearticles used to introduce claim recitations. In addition, even if aspecific number of an introduced claim recitation is explicitly recited,those skilled in the art will recognize that such recitation should beinterpreted to mean at least the recited number, e.g., the barerecitation of “two recitations,” without other modifiers, means at leasttwo recitations, or two or more recitations. Furthermore, in thoseinstances where a convention analogous to “at least one of A, B, and C,etc.” is used, in general such a construction is intended in the senseone having skill in the art would understand the convention, e.g., “asystem having at least one of A, B, and C” would include but not belimited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, etc. In those instances where a convention analogous to “atleast one of A, B, or C, etc.” is used, in general such a constructionis intended in the sense one having skill in the art would understandthe convention, e.g., “a system having at least one of A, B, or C” wouldinclude but not be limited to systems that have A alone, B alone, Calone, A and B together, A and C together, B and C together, and/or A,B, and C together, etc. It will be further understood by those withinthe art that virtually any disjunctive word and/or phrase presenting twoor more alternative terms, whether in the description, claims, ordrawings, should be understood to contemplate the possibilities ofincluding one of the terms, either of the terms, or both terms. Forexample, the phrase “A or B” will be understood to include thepossibilities of “A” or “B” or “A and B.”

From the foregoing, it will be appreciated that various implementationsof the present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various implementations disclosed herein are notintended to be limiting, with the true scope and spirit being indicatedby the following claims.

What is claimed is:
 1. A method, comprising: receiving, by a processorof an processor, a message with a back-off timer from a network node;determining, by the processor, whether a single-network slice selectionassistance information (S-NSSAI) of a protocol data unit (PDU) sessionis provided by the network node; starting, by the processor, theback-off timer; and associating, by the processor, the back-off timerwith the S-NSSAI of the PDU session in an event that the S-NSSAI isprovided by the network node.
 2. The method of claim 1, furthercomprising: transmitting, by the processor, a request message to thenetwork node, wherein the request message comprises at least one of aPDU session establishment request, a PDU session modification request,and a PDU session release request.
 3. The method of claim 1, wherein themessage comprises at least one of a PDU session establishment reject, aPDU session modification reject, and a PDU session release command. 4.The method of claim 1, wherein the S-NSSAI is a current or latestS-NSSAI of the PDU session.
 5. The method of claim 1, furthercomprising: transmitting, by the processor, a PDU session establishmentrequest message with a valid S-NSSAI or no S-NSSAI to the network node.6. The method of claim 1, further comprising: transferring, by theprocessor, from a first public land mobile network (PLMN) to a secondPLMN; and receiving, by the processor, the S-NSSAI associated with thesecond PLMN from the network node.
 7. The method of claim 1, wherein themessage comprises a 5^(th) generation session management (5GSM) causevalue #67 which represents insufficient resources for a specific sliceand data network name (DNN) or a 5GSM cause value #69 which representsinsufficient resources for a specific slice.
 8. The method of claim 1,wherein the back-off timer comprises at least one of a congestionback-off timer T3584 and a congestion back-off timer T3585.
 9. A method,comprising: receiving, by a processor of an processor, a message with aback-off timer from a network node; starting, by the processor, theback-off timer associated with a single-network slice selectionassistance information (S-NSSAI) of a protocol data unit (PDU) session;determining, by the processor, whether an S-NSSAI of a request messageis the S-NSSAI associated with the back-off timer; and forbidding, bythe processor, a transmission of the request message in an event thatthe S-NSSAI of the request message is the S-NSSAI associated with theback-off timer.
 10. The method of claim 9, wherein the request messagecomprises at least one of a PDU session establishment request and a PDUsession modification request.
 11. The method of claim 10 wherein theS-NSSAI of the request is the S-NSSAI associated with the PDU sessionestablishment request message, or the S-NSSAI of the PDU sessionassociated with the PDU session modification request message.
 12. Themethod of claim 10, wherein the S-NSSAI of the request is the mappedhome public land mobile networks (HPLMN) S-NSSAI associated with the PDUsession establishment request message, or the mapped HPLMN S-NSSAI ofthe PDU session associated with the PDU session modification requestmessage.
 13. The method of claim 9, wherein when the back-off timer isapplied in all public land mobile networks (PLMNs), the S-NSSAI of therequest message comprises a mapped home PLMN (HPLMN) S-NSSAI of the PDUsession or a mapped HPLMN S-NSSAI of the PDU session establishmentrequest, and wherein the S-NSSAI associated with the back-off timercomprises a mapped home PLMN (HPLMN) S-NSSAI.
 14. The method of claim 9,wherein when the back-off timer is applied in all public land mobilenetworks (PLMNs), the S-NSSAI of the request message comprises a homePLMN (HPLMN) S-NSSAI or serving PLMN S-NSSAI of the PDU session or aHPLMN S-NSSAI or serving PLMN S-NSSAI of the PDU session establishmentrequest, and wherein the S-NSSAI associated with the back-off timercomprises a mapped home PLMN (HPLMN) S-NSSAI.
 15. The method of claim 9,wherein when the back-off timer is applied in a registered public landmobile networks (RPLMN), the S-NSSAI of the request message comprises anS-NSSAI of the PDU session or an S-NSSAI of the PDU sessionestablishment request.
 16. An apparatus, comprising: a transceiverwhich, during operation, wirelessly communicates with a network node ofa wireless network; and a processor communicatively coupled to thetransceiver such that, during operation, the processor performsoperations comprising: receiving, via the transceiver, a message with aback-off timer from the network node; determining whether asingle-network slice selection assistance information (S-NSSAI) of aprotocol data unit (PDU) session is provided by the network node;starting the back-off timer; and associating the back-off timer with theS-NSSAI of the PDU session in an event that the S-NSSAI is provided bythe network node.
 17. The apparatus of claim 16, wherein, duringoperation, the processor further performs operations comprising:transmitting, via the transceiver, a request message to the networknode, wherein the request message comprises at least one of a PDUsession establishment request, a PDU session modification request, and aPDU session release request.
 18. The apparatus of claim 16, wherein themessage comprises at least one of a PDU session establishment reject, aPDU session modification reject, and a PDU session release command. 19.An apparatus, comprising: a transceiver which, during operation,wirelessly communicates with a network node of a wireless network; and aprocessor communicatively coupled to the transceiver such that, duringoperation, the processor performs operations comprising: receiving, viathe transceiver, a message with a back-off timer from the network node;starting the back-off timer associated with a single-network sliceselection assistance information (S-NSSAI) of a protocol data unit (PDU)session; determining whether an S-NSSAI of a request message is theS-NSSAI associated with the back-off timer; and forbidding atransmission of the request message in an event that the S-NSSAI of therequest message is the S-NSSAI associated with the back-off timer. 20.The apparatus of claim 19, wherein the request message comprises atleast one of a PDU session establishment request and a PDU sessionmodification request.